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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Cold Atomic Hydrogen, Narrow Self-Absorption, and the Age of Molecular Clouds

This viewgraph presentation reviews the history, and current work on HI and its importance in star formation. Through many observations of HI Narrow Self Absorption (HINSA) the conclusions are drawn and presented. Local molecular clouds have HI well-mixed with molecular constituents This HI is cold, quiescent, and must be well-shielded from the UV radiation field The density and fractional abundance (wrt H2) of the cold HI are close to steady state values The time required to convert these starless clouds from purely HI initial state to observed present composition is a few to ten million years This timescale is a lower limit - if dense clouds being swept up from lower density regions by shocks, the time to accumulate material to get A(sub v) is approximately 1 and provide required shielding may be comparable or longer

star formation↗
NASA NTRS2008

Spatially Resolved Imaging at 350 Micrometers of Cold Dust in Nearby Elliptical Galaxies

Continuum observations at 350 micrometers of seven nearby elliptical galaxies for which CO gas disks have recently been resolved with interferometry mapping are presented. These SHARC II mapping results provide the first clearly resolved far-infrared (FIR)-to-submillimeter continuum emission from cold dust (with temperatures 31 K is approximately greater than T approximately greater than 23 K) of any elliptical galaxy at a distance greater than 40 Mpc. The measured FIR excess shows that the most likely and dominant heating source of this dust is not dilute stellar radiation or cooling flows, but rather star formation that could have been triggered by an accretion or merger event and fueled by dust-rich material that has settled in a dense region cospatial with the central CO gas disks. The dust is detected even in two cluster ellipticals that are deficient in H (sub I), showing that, unlike H (sub I), cold dust and CO in ellipticals can survive in the presence of hot X-ray gas, even in galaxy clusters. No dust cooler than 20 K, either distributed outside the CO disks or cospatial with and heated by the entire dilute stellar optical galaxy (or very extended H (sub I)), is currently evident.

photometry↗
NASA NTRS2008

Cold Start of a Radiator Equipped with Titanium-Water Heat Pipes

Radiator panels utilizing titanium-water heat pipes are being considered for lunar applications. A traditional sandwich structure is envisioned where heat pipes are embedded between two high thermal conductivity face sheets. The heat pipe evaporators are to be thermally connected to the heat source through one or more manifolds containing coolant. Initial radiator operation on the lunar surface would likely follow a cold soak where the water in the heat pipes is purposely frozen. To achieve heat pipe operation, it will be necessary to thaw the heat pipes. One option is to allow the sunlight impinging on the surface at sunrise to achieve this goal. Testing was conducted in a thermal vacuum chamber to simulate the lunar sunrise and additional modeling was conducted to identify steady-state and transient response. It was found that sunlight impinging on the radiator surface at sunrise was insufficient to solely achieve the goal of thawing the water in the heat pipes. However, starting from a frozen condition was accomplished successfully by applying power to the evaporators. Start up in this fashion was demonstrated without evaporator dryout. Concern is raised over thawing thermosyphons, vertical heat pipes operating in a gravity field, with no wick in the condenser section. This paper presents the results of the simulated cold start study and identifies future work to support radiator panels equipped with titanium-water heat pipes.

Jaworske, Donald A.↗
NASA NTRS2010

Investigation of Loop Heat Pipe Survival and Restart After Extreme Cold Environment Exposure

NASA plans human exploration near the South Pole of the Moon, and other locations where the environment is extremely cold. This paper reports on the heat transfer performance of a loop heat pipe (LHP) exposed to extreme cold under the simulated reduced gravitational environment of the Moon. A common method of spacecraft thermal control is to use a LHP with ammonia working fluid. Typically, a small amount of heat is provided either by electrical heaters or by environmental design, such that the LHP condenser temperature never drops below the freezing point of ammonia. The concern is that a liquid-filled, frozen condenser would not restart, or that a thawing condenser would damage the tubing due to the expansion of ammonia upon thawing. This paper reports the results of an experimental investigation of a novel approach to avoid these problems. The LHP compensation chamber (CC) is conditioned such that all the ammonia liquid is removed from the condenser and the LHP is nonoperating. The condenser temperature is then reduced to below that of the ammonia freezing point. The LHP is then successfully restarted.

Golliher, Eric↗
NASA NTRS2011

Discovery and Mass Measurements of a Cold, Sub-Neptune Mass Planet and Its Host Star

The gravitational microlensing exoplanet detection method is uniquely sensitive to cold, low-mass planets which orbit beyond the snow-line, where the most massive planets are thought to form. The early statistical results from microlensing indicate that Neptune-Saturn mass planets located beyond the snow-line are substantially more common than their counterparts in closer orbits that have found by the Doppler radial velocity method. We present the discovery of the planet MOA-2009-BLG-266Lb, which demonstrates that the gravitational microlensing method also has the capability to measure the masses of cold, low-mass planets. The mass measurements of the host star and the planet are made possible by the detection of the microlensing parallax signal due to the orbital motion or the Earth as well as observations from the EPOXI spacecraft in a Heliocentric orbit. The microlensing light curve indicates a planetary host star mass of M(sun) = 0.54 + / - 0.05M(sun) located at a distance of DL= 2.94 _ 0.21 kpc, orbited by a planet of mass mp= 9.8 +/-1.1M(Earth) with a semi-major axis of a = 3.1(+1.9-0.4)MAU.

Barry, Richard K., Jr.↗
NASA NTRS2006

Mobile Robot for Exploring Cold Liquid/Solid Environments

The Planetary Autonomous Amphibious Robotic Vehicle (PAARV), now at the prototype stage of development, was originally intended for use in acquiring and analyzing samples of solid, liquid, and gaseous materials in cold environments on the shores and surfaces, and at shallow depths below the surfaces, of lakes and oceans on remote planets. The PAARV also could be adapted for use on Earth in similar exploration of cold environments in and near Arctic and Antarctic oceans and glacial and sub-glacial lakes.

Bergh, Charles↗
NASA NTRS2011

Challenges of Cold Conditioning and Static Testing the Second Ares Demonstration Motor (DM-2)

On August 31, 2010, a five-segment demonstration motor (DM) for the Ares program was successfully tested. A series of demonstration motors (DMs) will be tested in different conditioned environments to confirm they meet their design specifications. The second demonstration motor (DM-2) was the first cold motor. The motor needed to be subjected to sub-freezing temperatures for two months so that its internal propellant mean bulk temperature (PMBT) was approximately 40 F. Several challenges had to be overcome to make this a successful test. One challenge was to condition four field joints to get the O-rings approximately 32 F. This would be done by applying conditioning shrouds to externally cool each field joint after the test bay was pulled off. The purpose of this conditioning was to validate the new O-ring design and allow joint heaters to be eliminated. Another challenge was maintaining temperature requirements for components in the nozzle vectoring system. A separate heating system was used to warm these components during cold conditioning. There were 53 test objectives that required 764 channels of data to be recorded; 460 were specific to DM-2. This instrumentation had to be installed prior to conditioning, which meant the baseline process and timeline had to be modified to meet this time critical schedule.

Quinn, Shyla↗
NASA NTRS2004

Laboratory Apparatus Generates Dual-Species Cold Atomic Beam

A laser cooling apparatus that generates a cold beam of rubidium and cesium atoms at low pressure has been constructed as one of several intermediate products of a continuing program of research on laser cooling and atomic physics. Laser-cooled atomic beams, which can have temperatures as low as a microkelvin, have been used in diverse applications that include measurements of fundamental constants, atomic clocks that realize the international standard unit of time, atom-wave interferometers, and experiments on Bose-Einstein condensation. The present apparatus is a prototype of one being evaluated for use in a proposed microgravitational experiment called the Quantum Interferometric Test of Equivalence (QuITE). In this experiment, interferometric measurements of cesium and rubidium atoms in free fall would be part of a test of Einstein s equivalence principle. The present apparatus and its anticipated successors may also be useful in other experiments, in both microgravity and normal Earth gravity, in which there are requirements for dual-species atomic beams, low temperatures, and low pressures. The apparatus includes a pyramidal magneto-optical trap in which the illumination is provided by multiple lasers tuned to frequencies characteristic of the two atomic species. The inlet to the apparatus is located in a vacuum chamber that contains rubidium and cesium atoms at a low pressure; the beam leaving through the outlet of the apparatus is used to transfer the atoms to a higher-vacuum (lower-pressure) chamber in which measurements are performed. The pyramidal magneto-optical trap is designed so that the laser cooling forces in one direction are unbalanced, resulting in a continuous cold beam of atoms that leak out of the trap (see figure). The radiant intensity (number of atoms per unit time per unit solid angle) of the apparatus is the greatest of any other source of the same type reported to date. In addition, this is the first such apparatus capable of producing a slow, collimated beam that contains two atomic species at the same time.

Thompson, Robert↗
NASA NTRS2012

Herschel Discovery of a New class of Cold, Faint Debris Discs

We present Herschel PACS 100 and 160 micron observations of the solar-type stars alpha Men, HD 88230 and HD 210277, which form part of the FGK stars sample of the Herschel Open Time Key Programme (OTKP) DUNES (DUst around NEarby Stars). Our observations show small infrared excesses at 160 micron for all three stars. HD 210277 also shows a small excess at 100 micron. while the 100 micron fluxes of a Men and HD 88230 agree with the stellar photospheric predictions. We attribute these infrared excesses to a new class of cold, faint debris discs. alpha Men and HD 88230 are spatially resolved in the PACS 160 micron images, while HD 210277 is point-like at that wavelength. The projected linear sizes of the extended emission lie in the range from approximately 115 to <= 250 AU. The estimated black body temperatures from the 100 and 160 micron fluxes are approximately < 22 K, while the fractional luminosity of the cold dust is L(dust)/ L(star) approximates 10(exp -6), close to the luminosity of the Solar-System's Kuiper belt. These debris discs are the coldest and faintest discs discovered so far around mature stars and cannot easily be explained by invoking "classical" debris disc models.

Eiroa, C.↗
NASA NTRS2011

Fast Simulations of Gas Sloshing and Cold Front Formation

We present a simplified and fast method for simulating minor mergers between galaxy clusters. Instead of following the evolution of the dark matter halos directly by the N-body method, we employ a rigid potential approximation for both clusters. The simulations are run in the rest frame of the more massive cluster and account for the resulting inertial accelerations in an optimised way. We test the reliability of this method for studies of minor merger induced gas sloshing by performing a one-to-one comparison between our simulations and hydro+N-body ones. We find that the rigid potential approximation reproduces the sloshing-related features well except for two artefacts: the temperature just outside the cold fronts is slightly over-predicted, and the outward motion of the cold fronts is delayed by typically 200 Myr. We discuss reasons for both artefacts.

Roediger, E.↗
NASA NTRS2011

Herschel Discovery of a New Class of Cold, Faint Debris Discs

We present Herschel PACS 100 and 160 micron observations of the solar-type stars alpha Men, HD 88230 and HD 210277, which form part of the FGK stars sample of the Herschel Open Time Key Programme (OTKP) DUNES (DUst around NEarby Stars). Our observations show small infrared excesses at 160 m for all three stars. HD 210277 also shows a small excess at 100 micron, while the 100 micron fluxes of alpha Men and HD 88230 agree with the stellar photospheric predictions. We attribute these infrared excesses to a new class of cold, faint debris discs. alpha Men and HD 88230 are spatially resolved in the PACS 160 m images, while HD 210277 is point-like at that wavelength. The projected linear sizes of the extended emission lie in the range from approx 115 to <= 250 AU. The estimated black body temperatures from the 100 and 160 micron fluxes are approx < 22 K, while the fractional luminosity of the cold dust is L(sub dust) / L(*) approx 10 (exp 6) close to the luminosity of the Solar-System's Kuiper belt. These debris discs are the coldest and faintest discs discovered so far around mature stars and cannot easily be explained by invoking "classical" debris disc models.

Eiroal, C.↗
NASA NTRS2012

Fast Simulations of Gas Sloshing and Cold Front Formation

We present a simplified and fast method for simulating minor mergers between galaxy clusters. Instead of following the evolution of the dark matter halos directly by the N-body method, we employ a rigid potential approximation for both clusters. The simulations are run in the rest frame of the more massive cluster and account for the resulting inertial accelerations in an optimised way. We test the reliability of this method for studies of minor merger induced gas sloshing by performing a one-to-one comparison between our simulations and hydro+N-body ones. We find that the rigid potential approximation reproduces the sloshing-related features well except for two artifacts: the temperature just outside the cold fronts is slightly over-predicted, and the outward motion of the cold fronts is delayed by typically 200 Myr. We discuss reasons for both artifacts.

Roediger, E.↗
NASA NTRS2012

Cold Fronts in Clusters of Galaxies: Observations and Modeling

Mergers of galaxy clusters -- some of the most energetic events in the Universe -- produce disturbances in hot intracluster medium, such as shocks and cold fronts, that can be used as tools to study the physics of galaxy clusters. Cold fronts may constrain viscosity and the structure and strength of the cluster magnetic fields. Combined with radio data, these observations also shed light on the production of ultrarelativistic particles that are known to coexist with the cluster thermal plasma. This talk will summarize the current X-ray observations of cluster mergers, as well as some recent radio data and high resolution hydrodynamic simulations.

Markevitch, Maxim↗
NASA NTRS2013

Herschel's "Cold Debris Disks": Background Galaxies or Quiescent Rims of Planetary Systems?

Infrared excesses associated with debris disk host stars detected so far peak at wavelengths around approx, 100 micron or shorter. However, 6 out of 31 excess sources studied in the Herschel Open Time Key Programme, DUNES, have been seen to show significant-and in some cases extended-excess emission at 160 micron, which is larger than the 100 micron excess. This excess emission has been attributed to circumstellar dust and has been suggested to stem from debris disks colder than those known previously. Since the excess emission of the cold disk candidates is extremely weak, challenging even the unrivaled sensitivity of Herschel, it is prudent to carefully consider whether some or even all of them may represent unrelated galactic or extragalactic emission, or even instrumental noise. We re-address these issues using several distinct methods and conclude that it is highly unlikely that none of the candidates represents a true circumstellar disk. For true disks, both the dust temperatures inferred from the spectral energy distributions and the disk radii estimated from the images suggest that the dust is nearly as cold as a blackbody. This requires the grains to be larger than approx. 100 micron, even if they are rich in ices or are composed of any other material with a low absorption in the visible. The dearth of small grains is puzzling, since collisional models of debris disks predict that grains of all sizes down to several times the radiation pressure blowout limit should be present. We explore several conceivable scenarios: transport-dominated disks, disks of low dynamical excitation, and disks of unstirred primordial macroscopic grains. Our qualitative analysis and collisional simulations rule out the first two of these scenarios, but show the feasibility of the third one. We show that such disks can indeed survive for gigayears, largely preserving the primordial size distribution. They should be composed of macroscopic solids larger than millimeters, but smaller than a few kilometers in size. If larger planetesimals were present, then they would stir the disk, triggering a collisional cascade and thus causing production of small debris, which is not seen. Thus, planetesimal formation, at least in the outer regions of the systems, has stopped before "cometary" or "asteroidal" sizes were reached.

Herschel↗
NASA NTRS2015

Global Precipitation Measurement Cold Season Precipitation Experiment (GCPEx): For Measurement Sake Let it Snow

As a component of the Earth's hydrologic cycle, and especially at higher latitudes,falling snow creates snow pack accumulation that in turn provides a large proportion of the fresh water resources required by many communities throughout the world. To assess the relationships between remotely sensed snow measurements with in situ measurements, a winter field project, termed the Global Precipitation Measurement (GPM) mission Cold Season Precipitation Experiment (GCPEx), was carried out in the winter of 2011-2012 in Ontario, Canada. Its goal was to provide information on the precipitation microphysics and processes associated with cold season precipitation to support GPM snowfall retrieval algorithms that make use of a dual-frequency precipitation radar and a passive microwave imager on board the GPM core satellite,and radiometers on constellation member satellites. Multi-parameter methods are required to be able to relate changes in the microphysical character of the snow to measureable parameters from which precipitation detection and estimation can be based. The data collection strategy was coordinated, stacked, high-altitude and in-situ cloud aircraft missions with three research aircraft sampling within a broader surface network of five ground sites taking in-situ and volumetric observations. During the field campaign 25 events were identified and classified according to their varied precipitation type, synoptic context, and precipitation amount. Herein, the GCPEx fieldcampaign is described and three illustrative cases detailed.

GCPEx↗
NASA NTRS2015

Resource Prospector Propulsion System Cold Flow Testing

Resource Prospector (RP) is a NASA mission being led by NASA Ames Research Center with current plans to deliver a scientific payload package aboard a rover to the lunar surface. As part of an early risk reduction activity, Marshall Space Flight Center (MSFC) and Johnson Space Flight Center (JSC) have jointly developed a government-version concept of a lunar lander for the mission. The spacecraft consists of two parts, the lander and the rover which carries the scientific instruments. The lander holds the rover during launch, cruise, and landing on the surface. Following terminal descent and landing the lander portion of the spacecraft become dormant after the rover embarks on the science mission. The lander will be equipped with a propulsion system for lunar descent and landing, as well as trajectory correction and attitude control maneuvers during transit to the moon. Hypergolic propellants monomethyl hydrazine and nitrogen tetroxide will be used to fuel sixteen 70-lbf descent thrusters and twelve 5-lbf attitude control thrusters. A total of four metal-diaphragm tanks, two per propellant, will be used along with a high-pressure composite-overwrapped pressure vessel for the helium pressurant gas. Many of the major propulsion system components are heritage missile hardware obtained by NASA from the Air Force. In parallel with the flight system design activities, a simulated propulsion system based on flight drawings was built for conducting a series of water flow tests to characterize the transient fluid flow of the propulsion system feed lines and to verify the critical operation modes such as system priming, waterhammer, and crucial mission duty cycles. The primary objective of the cold flow testing was to simulate the RP propulsion system fluid flow operation through water flow testing and to obtain data for anchoring analytical models. The models will be used to predict the transient and steady state flow behaviors in the actual flight operations. All design and build efforts, including the analytical modeling, have been performed. The cold flow testing of the propulsion system was set up and conducted at a NASA MSFC test facility. All testing was completed in the summer of 2014, and this paper documents the results of that testing and the associated fluid system modeling efforts.

Williams, Hunter↗
NASA NTRS2016

Cold Helium Pressurization for Liquid Oxygen/Liquid Methane Propulsion Systems: Fully-Integrated Hot-Fire Test Results

Hot-fire test demonstrations were successfully conducted using a cold helium pressurization system fully integrated into a liquid oxygen (LOX) / liquid methane (LCH4) propulsion system (Figure 1). Cold helium pressurant storage at near liquid nitrogen (LN2) temperatures (-275 F and colder) and used as a heated tank pressurant provides a substantial density advantage compared to ambient temperature storage. The increased storage density reduces helium pressurant tank size and mass, creating payload increases of ~35% for small lunar-lander sized applications. This degree of mass reduction also enables pressure-fed propulsion systems for human-rated Mars ascent vehicle designs. Hot-fire test results from the highly-instrumented test bed will be used to demonstrate system performance and validate integrated models of the helium and propulsion systems. A pressurization performance metric will also be developed as a means to compare different active pressurization schemes.

Morehead, R. L.↗
NASA NTRS2016

Cold Helium Pressurization for Liquid Oxygen / Liquid Methane Propulsion Systems: Fully-Integrated Initial Hot-Fire Test Results

A prototype cold helium active pressurization system was incorporated into an existing liquid oxygen (LOX) / liquid methane (LCH4) prototype planetary lander and hot-fire tested to collect vehicle-level performance data. Results from this hot-fire test series were used to validate integrated models of the vehicle helium and propulsion systems and demonstrate system effectiveness for a throttling lander. Pressurization systems vary greatly in complexity and efficiency between vehicles, so a pressurization performance metric was also developed as a means to compare different active pressurization schemes. This implementation of an active repress system is an initial sizing draft. Refined implementations will be tested in the future, improving the general knowledge base for a cryogenic lander-based cold helium system.

Morehead, R. L.↗